There are many uses for an array of densely-packed, discrete, metal microspheres supported on a substrate, particularly when the microspheres are deformable and conductive. The general areas in which such an array of metal microspheres can be used include electric circuits, micro-soldering, and imaging.
In the area of electric circuits, a so-called breadboard for the testing of electric circuits can be made by providing an array of discrete, densely-packed conductive, deformable, metal microspheres. An electric circuit can be formed in the array by tracing through the microsphere-coated surface with a sharp object. Electrical contact is made between the individual microspheres where pressure is applied, deforming the spheres and forming a desired electric pathway in the otherwise non-conductive surface. If desired, such a circuit can be preserved by coating the surface with a protective plastic or the like.
In a related application, a security film can be made by coating such an array of conductive, deformable metal microspheres with a protective cover film. Tampering is evidenced by the presence of regions of deformed spheres which may be detected visually or electrically.
Powders used for fine scale micro-soldering, currently produced by spray atomization, can be produced by removing the individual metal microspheres from a substrate. In addition, an entire array of metal microspheres can be used to deliver solder, for example, by placing such an array against a circuit and heating the back side of the substrate. When heated, the individual metal microspheres melt and are transferred as solder to the circuit.
An array of discrete, densely-packed, metal microspheres can be made which is useful in imaging. Such arrays are typically transparent and dull in appearance. When pressure is applied to the transparent, dull array of microspheres the array becomes opaque and shiny in the areas where pressure is applied. The degree of transparency and specular reflectance is dependent on the amount of pressure applied to the individual metal microspheres. Various useful images or patterns can be produced, for instance, by pressing an embossed surface against such an array of microspheres.
These and other important and varied uses for an array of densely-packed, discrete, metal microspheres, particularly microspheres which are deformable and conductive, has heretofore existed in the art. Therefore, a need exists to provide an array of densely-packed, discrete, metal microspheres on a substrate, preferably by a method which is commercially feasible. It is desirable that these metal microspheres be deformable and conductive and be extremely densely packed so that the array is useful for the end uses discussed above.